1,720,964 research outputs found
Morpho-Tectonic Evolution of the Southern Apennines and Calabrian Arc: Insights From Pollino Range and Surrounding Extensional Intermontane Basins
Full text linkThe evolution of topography in forearc regions results from the complex interplay of crustal and mantle processes. The Southern Apennines represent a well-studied forearc region that experienced several tectonic phases, initially marked by compressional deformation followed by extension and large-scale uplift. We present a new structural, geomorphic and fluvial analysis of the Pollino Massif and surrounding intermontane basins (Mercure, Campotenese and Castrovillari) to unravel their evolution since the Pliocene. We constrain multiple tectonic transport directions, evolution of the drainage, and magnitude and timing of long-term incision following base level falls. Two sets of knickpoints suggest two phases of base level lowering and allow to estimate similar to 500 m of long-term uplift (late Pleistocene), as observed in the Sila Massif. On a smaller spatial scale, the evolution and formation of topographic relief, sedimentation, and opening of intermontane basins is strongly controlled by the recent increase in rock uplift rate and fault activity. At the regional scale, an along-strike, long-wavelength uplift pattern from north to south can be explained by progressive lateral slab tearing and inflow of asthenospheric mantle beneath Pollino and Sila, which in turn may have promoted extensional tectonics. The lower uplift of Le Serre Massif may be explained as result of weak plate coupling due to narrowing of the Calabrian slab. The onset of uplift in the Pollino Massif, ranging from 400 to 800 ka, is consistent with that one proposed in the southern Calabrian forearc, suggesting a possible synchronism of uplift, and lateral tearing of the Calabrian slab.Topographic evolution constrained by structural, geomorphic and river analysis of the Pollino range and surrounding extensional basins At short spatial scale, increase in rock uplift and fault activity controls the endorheic-exorheic transition At regional scale, uplift increases between 400 and 800 ka, due to progressive lateral slab tearing, and inflow asthenospheric mantl
Post glacial sediment partitioning on a tectonically controlled, narrow shelf (Calabro-Tyrrhenian margin, Italy). Issues in defining S2S budget
Full text linkThe re-analysis of high-resolution seismic profiles collected along the narrow (2–9 km) shelf facing ∼90 km of the Calabro-Tyrrhenian coastline has enabled the reconstruction of its sequence-stratigraphic architecture, along with the quantification of sediment volumes accommodated during the last post-glacial sea level rise and highstand. The shelf volumes are compared with the gross volumes supplied by the short and steep rivers draining the uplifted hinterland area, obtained from morphometric analysis and inferred denudation rates (derived from uplift rates) of the drainage basins. The study area is divided in two main sectors based on the different morpho-stratigraphic setting and fluvial network controlling sediment distribution on the shelf. The Coastal Range sector is characterized by closely spaced mountainous rivers and narrow coastal plains; on the shelf, the post-LGM deposits show a main depocenter (up to 60 m thick) elongated ∼27 km parallel to the coastline. This shelf sector hosts up to 80% of the sediment sourced from rivers, with a small percentage of sediment loss, mainly related to off-shelf export along a network of shelf-indenting submarine canyons. Sediment deficit due to river aggradation is considered negligible based on the narrow and V-shaped thalwegs typical of the rivers in this sector. The Santa Eufemia sector is characterized by larger rivers and a wider coastal plain, with a major depocenter (up to 50 m thick) confined off the Amato River. In this sector, the entire post-LGM sequence accounts only for about 30% of the sediment supplied by rivers (60% considering only the HST), indicating that, in addition to sediment exported off-shelf, a significant part is trapped by river aggradation within the coastal plain. The volumetric comparison has also evidenced local but significant discrepancies in sedimentary budget between adjacent sub-sectors, likely related to the effect of northward-directed shelf currents on sediment distribution along the shelf
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Widespread mass-wasting processes off NE sicily (Italy). Insights from morpho-bathymetric analysis
Full text linkThe NE Sicilian continental margin is largely affected by canyons and related landslide scars. Two main types of submarine canyons are recognizable: The first type carves the shelf up to depths <20 m, a few hundred metres from the coast, acting as a main collector for sediments transported by hyperpycnal flows and/or littoral drift. These canyons mostly have a V-shaped cross-section and are characterized by a strong axial incision, where a network of dendritic gullies carving the canyon flanks converges. The second type of canyon occurs where the shelf is wider, hindering the direct connection between the subaerial and submarine drainage system. This setting exhibits canyon heads mostly confined to the shelf break, characterized by a weaker axial incision of the canyon and U-shaped cross-section. A total of 280 landslide scars are recognized in the study area and these are divided into three groups according to their morphology and location. A morphometric analysis of these scars is performed to investigate which parameters might be key factors in controlling instability processes and how they correlate with each other. We also try to assess the possible tsunamigenic potential associated with these landslide events by coupling the morphometric analysis with semi-empirical relationships available in the literature
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Lithological control on topographic relief evolution in a slow tectonic setting (Anti-Atlas, Morocco)
No full textTopographic relief results from the complex interactions between tectonics and erosional surface processes, which are primarily mediated by bedrock erodibility and climatic conditions. Ancient orogens offer a favourable setting to isolate the contribution of lithology, as tectonically driven rock uplift is typically negligible and rock strength variability can exert a critical role on the evolution of the topography. The Anti-Atlas in NW Africa is a late Paleozoic orogen comprising a well-preserved, elevated, relict landscape delimited by non-lithological knickpoints, that was uplifted during a regional late Cenozoic phase of topographic rejuvenation. Here, we combine a geomorphic analysis with 10Be-derived denudation rates to quantify bedrock erodibility and get insight into the surface evolution of the Anti-Atlas and the adjacent Siroua Massif. Specifically, we show that 10Be basin-wide denudation rates for the relict landscape are rather uniform and range from 5 to 12 m/Myr. These rates agree with long-term rates estimated from different methods suggesting that the relict topography archives erosional quasi-erosional steady-state conditions at least since the latest Cretaceous. The uniformly low 10Be denudation rates in the relict topography are consistent despite the variability in channel steepness and topographic relief that correlates with changes in rock type. The expansion of this analysis to the denudation rates of the downstream portion of the landscape, allows to demonstrate a linear relationship between denudation and channel steepness for catchments draining quartz bearing lithologies. This provides the chance to constrain a narrow range of bedrock erodibility values for different rock-types (quartzite, granitic and sedimentary rocks). These values are comparable with estimates from other slowly deforming settings. Specifically, our compilation from tectonically inactive to slow tectonic regions indicates that bedrock erodibility does not change significantly across different climatic zones and precipitation regimes. This highlights the critical role of lithology in controlling the production of topographic relief in post-orogenic/slow tectonic settings. Finally, we calculate the predicted denudation rates for the steeper portions of the landscape that adjusted to the new uplift rates based on the linear correlation between erosion rates and normalized steepness indices. These rates range from 20 to 50 m/Myr and agree with the direct measurements from two catchments
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